本文利用事件分析的标准方法检验了中国股票市场B股上市对A股价格的影响。本文发现 ,A股上市企业在B股招股公布前价格出现明显的正超额收益 ,但上市后就大幅下跌 ,主要原因在于投资者预期收益随着市场分割程度的降低和投资者数量的增加而下降。与国外情况不同的是 ,B股上市后A股流动性降低也是导致价格下跌的原因之一。这说明国内企业管理层双重上市的主要目的不是为了增加股东价值 ,而存在其他的非经济利益的考虑 This paper uses the standard method of event analysis to test the impact of the B-share listing on the A-share prices in the Chinese stock market. This paper finds that A-share listed companies have obvious positive excess returns before the announcement of B-share IPO, but dropped sharply after listing. The main reason is that the expected return of investors decreases with the decrease of market segmentation and the increase of investors . The difference with the foreign situation is that the decrease in liquidity of A-shares after the B-share listing is also one of the reasons for the price drop. This shows that the main purpose of the dual listing of domestic enterprise management is not to increase shareholder value, but to consider other non-economic benefits